The aim of the present retrospective study was to uncover the factor(s) responsible for the poor outcome of cadaver kidney grafts from female donors in male recipients. The 741 transplantations performed at our center from August 1983 to September 1997 were distributed into four groups according to recipient and donor gender: female donor to female recipient (F to F: n = 117, male donor to female recipient (M to F: n = 172), female donor to male recipient (F to M: n = 170), and male donor to male recipient (M to M: n = 282). All the patients received immunosuppressive therapy based on corticosteroids and cyclosporine, associated or not with either azathioprine or prophylactic anti-lymphocyte globulin. Overall graft survival was lower in the F to M group than in the three other groups (p = 0.009). Failures due to rejection were more frequent during the Ist post-transplant trimester in female than in male donor grafts, irrespective of recipient gender (p = 0.025). All failures due to technical problems occurred during the first 3 months post-transplantation: they were more frequent in the F to M group than in the three other groups (p = 0.040); this could be related to the older age of the donors in the former group. After the first post-transplant year, failures due to causes other than rejection remained low in the F to F group but increased steadily in the three other groups (p = 0.007). Specific survival rates were not correlated with the time-evolution of mean serum creatinine values, daily doses and trough levels of cyclosporine in the four groups of grafts. In conclusion, the poor outcome of F to M grafts results from combined immunologic and technical factors exerting their effects early in the course of transplantation.